This invention relates generally to tools for use in well bores and the like. More particularly, but not by way of limitation, this invention relates to an improved slip release apparatus for use with a packer that is disposed in a well bore.
Well tools slips of the type to which the present invention appertains are illustrated in U.S. Pat. No. 3,548,936, issued Dec. 22, 1970 to M. D. Kilgore et al. The slips referred to, are of unitary construction and maybe described as being generally tubular or cylindrical. The slips are provided with wall engaging or gripping teeth on diagonally opposite ends thereof which ends are separated by a distance that is greater than the diameter of the pipe or well in which the tool is to be used. Upon pivotal movement of such slips about the tool, the wall engaging teeth are moved into engagement with the well bore wall and become firmly embedded therein. To release such slips in the event that the tool is to be removed from the well bore is to be or moved therein, the U.S. Pat. No. 3,548,936 discloses the use of a lug or lugs carried by the slip carrier which are moved into engagement with a shoulder formed adjacent to the periphery of such slips and an upward pull is exerted thereon to rotate the slips from the set position into the unset or retracted position.
In the current designs, the force or pull is exerted directly upwardly into the upper teeth of the slip. In order to move one of the slips to the unset position, the metal of the well pipe or of the slip teeth must be sheared. Shearing of either requires a great deal of force.
In an effort to alleviate the amount of force required for release, a modified form of the slip releasing mechanism is illustrated in U.S. Pat. No. 3,379,314, which issued on Dec. 18, 1973 to N. W. Reed. The releasing apparatus described therein illustrates the use of a dog carried by the releasing lug which extends upwardly into a slot in the slip adjacent to the upper teeth. Upon engagement of the dog with well bore wall and with the slip, the force imparted to the slip tends to pivot the slip and thus reduce the shearing action previously described.
The foregoing methods of releasing the slip have word satisfactorily, but each requires a substantial amount of force.